This invention provides a drill which is directly applicable to geologic or geotechnical investigations where information and data on soil or rock are required. In particular, the arrangement described herein provides a portable, lightweight and mobile drill with capability for both efficient soil augering and rock coring, typically in remote areas where most mineral exploration is carried out; where access is limited due to non existent or limited road access; where low load-bearing soils typically cannot support heavy equipment, and other features such as dense bush, swamps and steep slopes make access difficult or impossible. This drill can also be used for other applications such as geotechnical (engineering), shallow groundwater and soil investigations.
In mineral exploration, soil sampling of overburden deposits where soils are overlying rock, also often referred to as till sampling, is increasingly being used as a tool in the search for minerals, precious stones and precious metals. This is due to a number of factors, including advancements in knowledge of mineral deposit features and relationship to glaciation, the capability of analytical laboratories to conduct and provide concise details on soil grain properties and composition and the increased costs of completing traditional core drilling investigations such as diamond drilling. Soil sampling and the subsequent analytical data can be used to improve understanding of surficial geologic environments which may provide important clues to the presence of underlying mineral deposits such as nickel, copper or precious stones such as diamonds.
Soil sampling for mineral exploration can be conducted using a variety of methods. The general purpose, however, is the same: to obtain a representative sample of soil and use the properties and composition to assist in gaining knowledge of the surface features and underlying hard rock environment.
Hand trenches, normally less than one meter width and less than two meters depth can be hand dug in overburden covered areas to expose the underlying bedrock for additional observation or rock sampling of the potential mineralized zone. This type of investigation is labour intensive, difficult, time consuming and often provides a rather limited exposure (view) of the bedrock. A similar type of excavation, known as borrow pits are also used for subsurface investigations.
At some locations, hand angering of boreholes typically 10-20 cm in diameter and up to a few meters depth is possible for reconnaissance type mineral investigations. However, this is also labour intensive and additional problems such as hole caving and intersection of pebbles or stones make it difficult to auger and sample at some locations.
Backhoe trenches, where possible, provide additional ease, depth and amount of exposure of bedrock compared to hand trenching. Most regular sized backhoes can provide trench or pit depths of 5-7 m and are often necessary where “channel” sampling, that is rock cut with a diamond blade and power saw, across a vein or in a sulphide exposure is required. However, due to the weight of such equipment, lack of roads, soft soils etc. it is often impractical to transport and use a backhoe for reconnaissance style or “quick look” prospecting at most locations where mineral exploration is conducted.
Augered boreholes using a machine driven auger can also be used. The surficial deposits that cover the underlying bedrock are variable dependent on the location and geologic processes that occurred in different regions. However, for much of Canada deposits of till, that is a mix of clay, silt, sand, gravel, cover the underlying bedrock. As glaciers advanced from Canada's north, large quantities of bedrock were gouged and the material imbedded in the ice only to be deposited at other locations as the glaciers retreated. Generally, the glacier advance directions can be determined from striations (gouges) in the bedrock. It is mainly the sampling and analysis of these till deposits that can provide prospectors with important clues as to the potential location of valuable ore deposits and precious stones such as diamonds. However, for large regions of the country, the till directly lying on bedrock is covered by lake sediments, of mainly clay and silt, which vary from 0 to 10's of m in depth. To obtain samples of the till overlying the bedrock, boreholes must first drilled through the sediments and then into the till.
The most efficient, cost effective and practical method for till prospecting is the recovery of soil samples using conveyor augers. Conveyor augers refer to the coupling of one auger onto another to form a continuous spiral that augers into soils and delivers the soil to ground surface where it can be sampled. These samples are also often referred to as “auger returns”.
On mineral claims or other prospective mineral areas, successful mineral zone delineation often requires numerous test boreholes, sometimes hundreds. Therefore, it is cost effective and time saving to have a lightweight, portable and mechanized soil drill for augering boreholes for till prospecting in remote locations.
Core Sampling or “Diamond Drilling” is also desirable in many cases. While most of Canada is covered by soil deposits, there are also areas where bed rock is near or exposed at surface and prospecting for minerals can be conducted by methods such as direct observation and sampling, geophysical measurements of rock properties and coring or diamond drilling into the bedrock. Coring is also referred to as “Diamond drilling” because the bits used to cut into the hard bedrock have diamonds encased in a metal matrix. Diamond is the hardest mineral and is best suited for use in drill bits for efficient coring of the softer rocks. Diamond drilling to test the rock is an important and necessary procedure for determining the concentration and quantity of mineralization and is used to determine if mineralized zones warrant additional exploration and expenditure. The procedure is more complex than soil augering and sampling and is normally completed after other less costly soil and surface rock sampling, geophysical surveys, and other tests have been completed to increase the chances of intersecting a prospective mineral zone with the diamond drilled boreholes.
Diamond drills consist of a power unit, normally diesel or gasoline engines, which engages a clutch and transmission unit, which in turn rotates the drill string consisting of: flush jointed drill rods that are coupled together; a core barrel; and a reaming shell with a diamond bit. The cylinder of cut rock or core advances into the core barrel as drilling progresses. The bit and core barrel and rods are rotated at higher speeds compared to soil augering and the drill cuttings are returned to surface by pumping water into the drill rods, core barrel and diamond bit. The rods are withdrawn from the borehole at regular intervals as the core barrel is filled with core. The core is retained in core boxes for a record of the type of rock intersected by the borehole.
As such, diamond drilling an important part of the exploration for minerals and a portable drill that has coring capability, in addition to soil augering is most useful for prospecting and exploration in remote areas.